Ionizing radiation increases intracellular production of reactive oxygen species, which can damage cell structure and function. The brain is particularly vulnerable to oxidative injury, and in an area-dependent manner. In order to elucidate differences in enzymatic antioxidative response of rat hippocampus and cortex, we measured activities of CuZnSOD, MnSOD, and CAT in those two brain regions, isolated 1 h and 24 h after exposure to 2 Gy of gamma-rays. Our results indicate that lower MnSOD activities and inducibility, found in the hippocampus, are probably some of the main reasons for the particularly great oxidative vulnerability of this brain region.